You can capture the brush form by special angle, and rotate it to a typical state by "angle 2" - this trick give you desired result. But actually - there is no option for gradient angle inside the brush form.

I definitely would want this feature- something more friendly for setting light/drop shadow fx. To get the (linear) gradient to flow the right direction for my use, I use the complex arrangement shown in the picture.

Alternately, I’d like to see gradient mapping translating form values into gradient mapped colors. Along that same process, would it be possible in the future to have forms using more than greyscale, so that forms can convey more information, such as depth of paint, normals, etc?

Along that same process, would it be possible in the future to have forms using more than greyscale, so that forms can convey more information, such as depth of paint, normals, etc?

This is not a pure black - it's an alpha map - black is opaque, gray is 50% transparent. white - is a 100% transparent... with other words - it's a depth of paint as you say. And to improve forms we only can add a color value to it.